The rod cells of vertebrate retinas are responsible for vision at low levels of light. The visual pigment, rhodopsin absorbs light as the primary visual event. This is followed by a series of events which leads to a hyperpolarization of the plasma membrane of the rod outer segment and results in a nerve impulse. This proposal deals with the molecular mechanisms of rhodopsin which are important in visual transduction. The asymmetric nature of rhodopsin in a new type of recombinant system will be exploited. An interesting feature of this system is its very low lipid to protein ratio. This characteristic may be responsible for special properties of the system and will be utilized to study the nature of protein-phospholipid interactions necessary for opsin regeneration. The nature of these interactions will be explored through the use of 31P NMR, 2D NMR and fluorescence depolarization. Symmetrical recombinants made via the dialysis method and the disc membrane will be used for comparative analysis. The size and the apparent tight packing of rhodopsn in the recombinant bilayer make it a reasonable system in which attempt three dimensional structural studies. An x-ray diffraction study will thus be attempted. It is anticipated that this new recombinant system will provide a model disc in terms of mimicking functions such as Ca ions release, and thus the role of rhodopsin in Ca ions release will be studied. The stabilization of the disk membrane bilayers with respect to the role of both protein (rhodopsin and opsin) and phospholipid composition will be examined. This information should be of value in understanding membrane degenerative diseases such as retinis pigmentosa.